# Copyright 2021 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the License);
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Copyright (c) Open-MMLab. All rights reserved.
from .hook import HOOKS, Hook


@HOOKS.register_module()
class DistSamplerSeedHook(Hook):

    def before_epoch(self, runner):
        if hasattr(runner.data_loader.sampler, 'set_epoch'):
            # in case the data loader uses `SequentialSampler` in Pytorch
            runner.data_loader.sampler.set_epoch(runner.epoch)
        elif hasattr(runner.data_loader.batch_sampler.sampler, 'set_epoch'):
            # batch sampler in pytorch warps the sampler as its attributes.
            runner.data_loader.batch_sampler.sampler.set_epoch(runner.epoch)
